Ultrasonic metal welding is a solid-state welding process that produces coalescence through the simultaneous application of localized high-frequency vibratory energy and moderate clamping forces. Ultrasonic welding of various materials is known and can be used to join dissimilar metals and can weld both thin sections and thin to thick sections. It can weld through most oxides and surface oils and creates negligible odor and fumes. Ultrasonic welding requires no welding consumables and is typically cost efficient. Energy consumption is low relative to resistance spot welding and variable costs are significantly lower than for self-pierce rivets.
Ultrasonic welding normally involves vibrating overlapping or adjacent workpieces clamped between a sonotrode and an anvil. Frictional forces occurring between the vibrating workpieces create a bond or weld that occurs at the interface between the workpieces, effectively joining them to one another.
Clinching is a low-cost, mechanical fastening process that can be used to join both similar and dissimilar materials of varying thickness. Clinching involves clamping the sheets in a die and using a punch to squeeze the sheets between the punch and the die causing sideways movement of the material to form an interlock or joint between the sheets. The process does not result in a heat-affected zone, requires no joining consumables, is characterized by long tool life and low maintenance requirements and does not require high current electrical systems. Clinching operations, however, employ large clamping forces, thereby requiring heavy equipment frames that can impose access limitations. In addition, clinch joints are characterized by lower peel and shear strengths than resistance spot welds and self-pierce riveted joints.
In addition, the clinching operation may require substantial deformation of the sheet material to be joined in order to form a proper bond. In some cases, the deformation can be particularly difficult, specifically when joining high-strength metal sheets, which tend to be more brittle and thus may develop cracks or stress in the joint area.
Therefore, there is a need in the art to provide an apparatus for joining two members or workpieces that utilizes or takes advantage of the benefits of both clinching and ultrasonic welding. Combining the use of ultrasonic energy with clinching overcomes limitations associated with traditional clinching operations and enhances ultrasonic metal welding capability. Accordingly, the combination of clinching and ultrasonic welding can reduce clamping force requirements, promote material flow and deformation and result in increased joint strength.